Piston Rings are getting narrower and thinner in order to reduce inertia and to improve sealing by allowing greater conformability to the cylinder bore. The top piston rings produced today are 1.2 to 1.5mm, with some as small as 1.0mm. Most oil piston rings are now in the 3.0mm size, and provide much less tension. The oil piston ring alone used to account for up to 25% of an engine's internal friction, but currently the number is down around 12-18%.
An area where changes are being made is in piston ring coatings, Chrome was the most common type of facing material for rings, then Molly was introduced and the followed by Plasma Sprayed Moly coatings.
Suzuki uses Nitriding to increase the wear resistance of their piston ring sets. Nitriding does not have the scuff resistance of plasma spray moly, but it eliminates the use of the chrome. Gas nitriding, which should not be confused with the black phosphate coating that is currently used on piston rings to prevent rust during shipping and storage, is a heat treatment process that impregnates the surface of the metal with nitrogen in order to harden the surface of the metal. This makes the piston rings very hard about 68 on the Rockwell C scale for improved wear resistance.
An advantage of the Plasma Spray Moly process is that different materials such as chrome carbide can be mixed with the moly powder to produce different ring characteristics.
Piston rings can be manufactured that don't wear, but they will wear the cylinder bore. A balance of piston ring and bore wear is the best solution to the problem.
Due to the high performance characteristics of Suzuki engines, for OEM fitment Suzuki uses ductile and steel top compression rings. these types of materials are required in order to withstand the pounding and heat. In addition the relocation of the top ring closer to the top of the piston, has required the use of ductile iron or steel top compression rings.
Ductile iron (nodular iron), has a different microstructure with rounded grains instead of rectangular grains. This allows the metal to bend without breaking , so it can withstand detonation in high load engines.
Chrome or moly faced ductile iron 1.5mm top compression rings have been in use since the 1980s, many premium ring sets now have ductile iron top rings.
Another ring material that is seeing greater use is steel. Twice as strong as ductile iron, steel can provide the durability and toughness needed for the most demanding top ring applications. Steel rings have a tensile strength in the range of 240,000 psi, which compares to 180,000 psi for ductile iron. Hardness can vary depending on the alloy and heat treatment, but is generally in the 44 to 53 HRC range compared to 38-40 HRC for ductile iron and 22-23 HRC for gray cast iron.
Like ductile iron, steel is not compatible with cast iron cylinder walls so it must be coated with either moly, or nitrided. Most of the steel rings currently in production have a width of 1.0 to 1.2mm, steel rings are usually barrel faced, having contoured outside diameters which give the ring a center contact with the cylinder wall.
My reconmendation here is to follow Suzuki's lead and replace ring sets with ones made of the same or better material, many piston ring manufacturers state that steel and ductile iron rings are virtually interchangeable. If a steel replacement ring is not available for a certain application that uses steel as original equipment, a ring set with ductile iron top rings can be substituted.